1. Field of the Invention
The present invention relates to an image forming apparatus of electro-photographic system such as copying machines, printers, etc, that is capable of efficient image forming when residual amount of toner to be supplied to electrostatic latent images formed on a photosensitive drum decreased.
2. Description of the Related Art
In a developing device used in an image forming apparatus of electro-photographic system for development using a so-called two-component developer comprising toner and carrier, toner density in the developing device is detected by an automatic toner sensor and according to the detected result, additional toner is supplied from a toner cartridge for maintaining the developing density at a desired level.
So far, residual toner amount in a toner cartridge was detected and when residual toner amount decreased to a specified near empty state, the near empty was displayed. In the case where a large volume of copying or printing was required, user once interrupts the image forming operation when recognized this near empty display, exchanged a toner cartridge. On the other hand, in the case of copying or printing of small volume, the image forming operation was continued and a toner cartridge was exchanged at the time when the toner empty was displayed.
Such the residual toner displayed device is similarly used in a cartridge type developing device using one-component toner. For example, an image forming apparatus that displays the number of residual formable sheets for the future by calculating the number of image sheets that are formable from residual tone amount for the future by detecting residual amount of one-component toner in a developing cartridge using an electrostatic capacity detecting system was disclosed in Japanese Patent Application No. 2001-83842. When the number of formable sheets is displayed, user exchanges a developing cartridge or supplies additional toner to the developing device according to the displayed device contents.
However, by such the conventional technology it is difficult to grasp whether a desired image forming operation can be made within residual toner amount, that is, within the number of formable image forming sheets before starting the image forming operation. In particular, when a desired image forming is for a large volume of original documents or it is desired to obtain a large amount of copies in the 2-in-1 mode or the 4-in-1 mode, even if the number of image formable sheets is simply displayed, user must compute and judge whether the desired image forming can be made within the displayed formable sheets.
Further, although the near toner empty is not displayed at the beginning when the image forming operation is started, the near toner empty may be displayed during the operation. In particular, if a desired image forming was voluminous, the near toner empty might be displayed during the operation in many cases and it was forced to interrupt the image forming operation. Further, when the operation was restarted, it became necessary to check the number of image formed copies already completed and reset the image forming conditions for remaining copies and thus, the operability of a copying machine could be lowered. Particularly, when the image forming operation is directed through a personal computer (PC) terminal such as a printer or when user was left from a copying machine in copying a large amount of sheets, user was not aware of the interruption of the image forming operation and a copying machine was left in the interrupted state and its productive could be lowered.
Accordingly, it is possible for user to easily recognize whether a desired image forming operation that is going to start is within residual toner amount before starting the image forming operation. When toner becomes empty during the operation, it is desired to urge user to take action for avoiding the interruption before starting the image forming operation and avoid the interruption of the operation, thereby improving operability and productivity.
An object of the present invention is to provide an image forming apparatus that has high operability as well as productivity by urging user to take action to avoid the image forming operation from being interrupted during the operation for empty of toner prior to starting the image forming operation.
According to the embodiment of the present invention, an image forming apparatus is provided. This image forming apparatus comprises: a developing device to form a positive image by supplying toner to an image carrier; a residual toner amount detecting unit to detect residual toner amount that can be supplied from the developing device; a comparing unit to compare a set toner consumption that is consumed under set image forming conditions with the residual toner amount; an advance warning signal output unit to generate an advance warning signal for generation of interruption during the image forming before starting the image forming under the set image forming conditions when the result of comparison by the comparing unit is (Set toner consumption) greater than (Residual toner amount); and a display device for displaying the advance warning signal for generation of interruption.
Further, according to the embodiment of the present invention, an image forming apparatus is provided. This image forming apparatus comprises: a developing device to form a developed image by supplying toner to an image carrier; a residual toner detecting unit to detect residual toner amount retained in the developing device; a comparing unit to comparing a set toner consumption that is consumed under set image forming conditions with the residual toner amount; a substitute condition changing unit to changing substitute image forming conditions to those that are approximate to the set image forming conditions when the result of comparison by the comparing unit is (Set toner consumption) greater than (Residual toner amount), that is, when the expected toner consumption is within the residual toner amount; and a display device to display the substitute image forming conditions.
Further, according to the embodiment of the present invention, an image forming apparatus is provided. This image forming apparatus comprises: a toner cartridge containing toner; a developing device to forming a developed image by supplying the toner supplied from the toner cartridge to an image carrier; a residual toner amount detecting unit to detect residual toner amount in the toner cartridge; a comparing unit to compare set toner consumption that is consumed under the set image forming conditions with the residual toner amount; a substitute condition changing unit for changing the substitute image forming condition to substitute image forming conditions approximate to the set image forming conditions when the result of comparison by the comparing unit is (Set toner consumption) greater than (Residual toner amount), that is, when the expected toner consumption is within the residual toner amount, and a display device to displaying the substitute image forming conditions.